Anatomy

The scapula is a triangular, flat bone that lies along the posterior thoracic wall. The “plane of the scapula” at rest is approximately 30 to 40 degrees in the frontal plane and is tipped anteriorly by approximately 10 to 20 degrees. Its attachment to the axial skeleton involves the acromioclavicular and sternoclavicular joints and the clavicle, which acts as a strut.

The stability of the scapula depends mainly on the muscle attachments and their dynamic stabilizing functions. Seventeen muscles have their origin or insertion on the scapula. The subscapularis and the serratus anterior muscles lie between the scapula and the thoracic wall. Several bursae also exist around the scapula, between it and the chest wall. Anatomical bursae include the infraserratus and supraserratus bursa, and adventitial bursae can develop, particularly around the superomedial angle and the inferior angle.

Some experts believe that these occur as an adaptation to repetitive movements or abnormal mechanics around the scapula. Cadaveric studies have demonstrated anatomical variants involving the superomedial border and the inferior pole of the scapula, which may or may not contribute to clinical symptoms.